This application claims priority to an application entitled xe2x80x9cVariable Channel Device for Wideband CDMA Systemxe2x80x9d filed in the Korean Industrial Property Office on Oct. 20, 1998 and assigned Ser. No. 98-43931, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to a CDMA (Code Division Multiple Access) system, and in particular, to a variable channel device for a wideband CDMA system which can be used both in a base station and a radio terminal of a wideband CDMA WLL (Wireless Local Loop) system.
2. Description of the Related Art
A CDMA system multiplies user signals with unique codes to spread the user signals and then transmits the spread user signals on a single carrier frequency. At the receiving end, the received signals are despread and then demultiplied using the same code to retrieve the user signals. The CDMA system uses this spread band scheme to increase the frequency utilization efficiency, and further provides message encryption using codes to enhance the authentication process and to protect sensitive subscriber information.
In a CDMA system, a channel for transmitting a signal from a base station to a radio terminal is called a forward link, and a channel for transmitting a signal from the radio terminal to the base station is called a reverse link.
A wideband CDMA (hereinafter, referred to as xe2x80x9cW-CDMAxe2x80x9d) system has a channel spacing of 5 MHz or 10 MHz. A convolutional encoder is typically used for reducing errors in the transmission bits. Orthogonal codes are uniquely assigned to respective channels for identifying the forward link channels. The W-CDMA system employs a direct sequence spreading technique and supports a chip rate of 4.096 Mcps (chips per second). Each channel is transmitted by Binary Phase Shift Keying (BPSK) waveform, and thereafter is transmitted by Quadrature Phase Shift Keying (QPSK). Thus, the channel spacing can be spread at much higher spreading rates.
The W-CDMA channel structure is disclosed in RHEE, xe2x80x9cCDMA Cellular Mobile Communications and Network Securityxe2x80x9d, Chapter 9 and 10: Prentice Hall PTR, 1997. According to that reference, a channel for a W-CDMA system is classified into a power control and signaling (PCS) channel and a traffic channel. The PCS channel includes the reverse and forward pilot channels, and the signaling channels. The traffic channel includes an access channel, a sync channel, a paging channel, and a traffic channel for transmitting the actual data.
A brief description will be made hereinbelow with regard to a channel structure specified in xe2x80x9cRadio Access Standard V2.0 for WLLxe2x80x9d as proposed by Korea Electronics Telecommunications Research Institute (ETRI).
The reverse modulation channel of a radio terminal includes an access channel and a reverse traffic channel. The access channel is comprised of an access pilot channel and an access information channel. As shown in FIG. 1A, the input bits of the access pilot channel, which are all 0""s, are spread with a reverse link sequence Rc (101) and Hadamard codes H0 and H1 (102), and then converted to a final pilot signal through a baseband filter 103 and a carrier multiplier 104. As shown in FIG. 1B, information bits of the access channel (ACH) are spread after passing a convolutional encoder 107, a block interleaver 108, and a symbol repeater 109.
The reverse traffic channel is comprised of a pilot, a PCS channel, and a traffic channel. As shown in FIG. 2A, information bits of the PPCS channel are multiplexed by a multiplexer 201 before spreading. As shown in FIG. 2B, information bits of the reverse traffic channel (R-TCH) are spread after passing a convolutional encoder 213, a symbol puncturer 214, symbol repeaters 215 and 217, and a serial-to-parallel (S/P) converter 216.
The reverse traffic channel operating in a multi-signal mode is comprised of a pilot channel, a PCS channel, a reserve channel, and a plurality of reverse traffic channels. As shown in FIG. 3A, information bits of the pilot channel, the PCS channel, the reverse channel, and the signaling channel, which constitute the reverse traffic channel operating in the multi-signal mode, are multiplexed by a multiplexer 301 before spreading. As shown in FIGS. 3B and 3C, information bits of an nth (or mth) reverse traffic channel (R-TCH) are spread after passing a convolutional encoder 313 (or 323), a symbol puncturer 314 (or 324), symbol repeaters 315 and 317 (or 325 and 327) and an S/P converter 316 (or 326).
The access channel operating in a packet mode is comprised of an access pilot channel and a packet access channel. As shown in FIG. 4A, information bits of the access pilot channel are all 0""s. As shown in FIG. 4B, information bits of the packet access channel (PACH) are spread after passing a convolutional encoder 407, a block interleaver 408 and a symbol repeater 409.
The reverse traffic channel operating in the packet mode is composed of a pilot channel, a packet signaling channel, and a reverse packet traffic channel. As shown in FIG. 5A, information bits of the pilot channel and the packet signaling channel (PSCH) are multiplexed by a multiplexer 501 before spreading. As shown in FIG. 5B, information bits of the reverse packet traffic channel (R-PTCH) are spread after passing a convolutional encoder 512, a block interleaver 513, symbol repeaters 514 and 516, and an S/P converter 515.
A forward modulation channel of the base station is comprised of a pilot channel, a sync channel, a paging channel, a traffic channel, and a power control and signaling (PCS) channel. As shown in FIG. 6A, information bits of the pilot channel, which are all 0""s, are spread with a Hadamard code H0 (601) and a forward link I/Q-arm sequences Rc (602), and then converted to a final transmission signal s(t) while passing through a baseband filter 603 and a carrier multiplier 604. Furthermore, information bits of the sync channel are spread after passing a convolutional encoder 607, a block interleaver 608, an S/P converter 609, and a symbol repeater 610.
As shown in FIG. 6B, information bits of the paging channel are spread after passing a convolutional encoder 617, a block interleaver 618, an S/P converter 619, and a symbol repeater 620. As shown in FIG. 6C, information bits of the traffic channel are spread after passing a convolutional encoder 626, a symbol puncturer 627, a scramble code spreader 629, an S/P converter 630, and a symbol repeater 631. As shown in FIG. 6D, information bits of the signaling channel are spread after passing a convolutional encoder 638, a block interleaver 639 and a symbol repeater 640. Furthermore, information bits of the power control and reserve channel are spread after passing symbol repeaters 646 and 647. The signal on the signaling channel can be exchanged with the signal on the power control and reserve channel.
As shown in FIG. 6E, information bits of the forward packet traffic channel operating in the packet mode are spread after passing a convolutional encoder 646, a block interleaver 647, a scramble code spreader 649, an S/P converter 650, and a symbol repeater 651.
Constructing a channel device for a CDMA system having various channels as illustrated in FIGS. 1 through 6 is undesirable, especially if the channel devices are implemented in a single chip, such as an ASIC (Application Specific Integrated Circuit). The ASIC will experience decreased reliability and increased power consumption.
It is, therefore, one of the objects of the present invention to provide a variable channel device for a W-CDMA system, in which various channels share similar function blocks, and these shared function blocks are controlled by an external register.
In accordance with one aspect of the present invention, a PCS/PPCS variable channel device for a W-CDMA system comprises a frame quality indicator for receiving information bits of a reverse power control channel; a serial-to-parallel converter connected to the frame quality indicator; a first multiplexer connected to the frame quality indicator and the serial-to-parallel converter; a first symbol repeater connected to the first multiplexer; a second symbol repeater for repeating symbols of discontinuous transmission data for a reserve channel; a second multiplexer connected to receive the output of the frame quality indicator, the serial-to-parallel converter, information bits of a pilot channel and the second symbol repeater; a third symbol repeater connected to the second multiplexer; a convolutional encoder for receiving information bits for a signaling channel; a symbol puncturer connected to the convolutional encoder, an inserter connected to the symbol puncturer; a third multiplexer connected to the symbol puncturer and the inserter; a first time division multiplexer connected to receive information bits of the pilot channel, the first symbol repeater, the third symbol repeater and the third multiplexer, for outputting a reverse/PPCS (Pilot Power Control and Signaling) channel signal; a first AND gate connected to the third multiplexer and a PCS (Power Control and Signaling) select signal; a fourth symbol repeater for repeating symbols of discontinuous transmission data of the reserve channel; a second time division multiplexer connected to receive information bits for a forward power control channel and the fourth symbol repeater; a fifth symbol repeater connected to the second time division multiplexer; and, a second AND gate connected to the fifth symbol repeater and connected to receive the PCS select signal, for outputting a forward/PCS channel signal.
In accordance with another aspect of the present invention, a traffic variable channel device for a W-CDMA system comprises a convolutional encoder for receiving traffic information bits; a symbol puncturer connected to the convolutional encoder; an inserter connected to the symbol puncturer; a multiplexer connected to the inserter and the symbol puncturer; a scramble code generator for receiving a scramble code seed; an AND gate connected to the scramble code generator, and for receiving a scramble select signal and a forward/reverse select signal; and, a scramble code spreader connected to the multiplexer and the AND gate for generating a forward/reverse traffic channel signal.